Removable end closure for firearm receivers



Dec. 27, 1949 Filed NOV. 28, 1947 T. R. ROBINSON, JR

REMOVABLE END CLOSURE FOR FIREARM RECEIVERS WMV 2 Sheets-Sheet l Patented Dec. 27, 1949 Nlrso sr REMOVABLE END CLOSURE FOR FIREA'RM RECEIVERS Thomas R. Robinson, Jr., Newton, Conn., assignor to The Marlin Firearms Company, 'New Haven, Conn., a corporation -of Connecticut Application Novemberk 28, 1947, ySerial No. 788,529

(Cl. 'S9-e199) 1'9 Claims. 1

The present invention relates in general to firearms and more especially to an automatic self-loading firearm having a receiver provided with a removable end-closure.

An object of the invention is to provide an improved end-closure for iirearms which because,

of its simplicity of construction and novel arrangement of elements is both dependable and durable `and effects a great economy both in Space and in cost of manufacture.

A further object of the invention is to provide Vthe receiver of `a firearm with a removable end-closure and improved means for locking the end-closure in the receiver vsuch that its removal maybe effected only when .the firearm .is unV cocked.

A still further object of the invention is to provide an improved removable end-closure for the receiver of -a rearm lhaving improved lockingmeans cooperatively lassociated with the firing mechanism such `that the firearm may not be cocked while the end-closure is unlocked from the reeciver.

With the above and other objects in view, as will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanying drawings, in which certain modes oi .carrying out the present invention are shown for Yillustrative purposes:

Fig. 1 is a side elevation partly in section of the receiver of an automatic firearm embodying the improved end-closure of this invention and including a fragmentary portion of the barrel;

Fig. 2 is an enlarged fragmentary plan view of the end-closure in the ,horizontal plane of the section line 2-2 .of Fig. :l showing the end-closure locking-lugs in locking engagement with the receiver and the firing-plunger in its .cocked position;

Fig. 3 is an end elevation :of the end-closure on section line 3-3 .of Fig. 1;

Fig. 4 is a fragmentary plan view in section similar to Fig. 2 but with the ring-plunger .in its forward firing position;

Fig. 5 is a fragmentary -plan view in section similar to Fig. V2 but with the locking-lugs of the end-closure withdrawn from locking engagement with the receiver and the ming-plunger abutting the inner ends of the locking-lugs;

Fig. A6 is an enlarged -side elevation in section of the improved end-closure of this invention including the locking-lugs;

Fig. '7 is a front end elevation of the end-closure of '6 3 Fig. 8 is a bottom View of the end-closure of Fig. 6;

9 is a perspective view of the end-closure with a quarter-round section of its fourth quadrant removed to show its longitudinal recess and its transverse aperture; and

Fig. 10 is a perspective view of one of the locking-lugs of the end-closure.

Referring to the drawings which show an exemplary embodiment of the invention, the particular firearm shown for the purposes of illustrating the invention is an automatic self loading irearm of the type disclosed in my copending .application Ser. No. 766,663, led August 6, 19417, ynow Patent No. 2,454,885, and comprises in the main a receiver indicated generally at l5 and a barrel l5 xedly secured to the forward end thereof.

As shown especially well in Fig. 1, the receiver l5 comprises a substantially-cylindrical member preferably formed from a suitable length of tubular steel vstock and is open at its opposite ends. The interior .of the receiver constitutes a cylindrical ,chamber IT for the action or breech-bolt iB of the firearm; and 1a cylindrical sleeve-pon tion I9 rearwardly of the chamber ll for `the endclosure or receiver-plug indicated generally at 2 3. As `shown ,clearly in Fig. 1, in this particular firearm the action-.chamber Il comprises a rear .section 2i and a forward section 22, the latter being .of relatively-small diameter and formed .by securing a substantially-cylindrical bushing 23 of relatively-thick Wall section in the forward end of the receiver. The breechbolt 4:8 is likewise formed .of two sections of different vdiameters corresponding to the size and shape :of-the respective sections 2l and 22 of the Chamber` 1H, the forward reduced end 24 of the breech-,bolt :having a spring-retracted firing-pin 215.supportedV for longitudinal movement therein. The rear :end portion 26 of the breech-bolt is provided l with anaXial aperture 21 which gives. access to therear end of the firing-pin and which also .chambers .the forward end of the actionspring .218 .and the forwardly-projecting end of the firing-plunger 129. The latter is adapted to be held in its retracted cocked position as shown in Fig. '-1 by asear 3U mounted on `a pivot-pin in the--end-closure, -as hereinafter described, the firing-plunger 219 being-adapted to be thrust for- Wardl'y when-released bythe sear 3Q into engagement with the ring-pin 25 `by a firing-plunger spring 43i carried on the'plunger. The underside of the receiver is provided with a trigger-plate indicatedgenerally at '32 in which elements of the ring `mechanism are mounted.

The present invention is concerned primarily with the end-,closure 20 and the locking-means thereof `and their relationship to the ,action- 3 spring and firing-plunger, and hence the present disclosure will not be burdened with a detailed description of the receiver and breech-bolt nor the specific elements of the'ring mechanism.

For a more comprehensive disclosure of these elements of the firearm, reference may be had to a co-pending application.

' in the receiver.

Referring especially to Figs. 6 through 9, the

end-closure or receiver-plug 20 constitutes a solid cylindrical metal member having a longitudinal recess therein indicated generally at 33 comprising an axially-aligned cylindrical aperture 34 which intersects the front face or end of the receiver-plug and extends rearwardly thereof terminating in an end wall 35, the over-all length of the blind aperture 34 of the receiver-plug being substantially /6 the length thereof. The forward end of the blind aperture 34 is provided with a concentric cylindrical counterbore 36 of relatively-large diameter, the end wall of which is blended into the forward end-of the blind aperture 3d by a sloping stop-shoulder 3l, for the purpose hereinafter described, the-longitudinal dimension of the counterbore being slightly greater lthan 1/4 the length lof the blind aperture 34. The foregoing statements of the relative lengths of the blind aperture 34 and the counterbore of the receiver-plug are not to be taken asv specific dimensions of these elements, but as illustrative only vof their relative proportions.

Formed in the bottom of the receiver-plug in a vertical plane through its longitudinal Vaxis and symmetrical with respect thereto, is a longitudinal inverted-U-shaped Sear-slot 38 which intersects the front face of the plug and extends Y rearwardly thereof to a point substantially opposite the end wall 35 of theaperture 34. The Sear-slot 3B is preferably formed by a milling operation and, hence, the rear end wall 39 of the slot comprises a substantially-cylindrical surface of revolution.

rThe depth of the scar-slot V38 is such that the top thereof intersects the rear end of the counterbore 35 so as to remove from the rear edge thereof substantially all of that portion of the sloping shoulder 3l which blends the lower half of the counterbore with the forward end of the blind aperture 315, as indicated clearly in Fig. 6. The forward end of the scar-slot has a rearwardlyand-upwardly-sloping top wall 40 which serves as a shoulder adapted to be engaged by the upper end of the scar-spring 4l, as shown in Fig. 1, while the top wall of the rear end of the searslot constitutes a continuation of its rear end Vwall 35. The blind aperture 34, its counterbore 36 and the vertically-intersecting scar-slot 38 are hereinafter referred to for brevity as the longitudinal recess 33 of thereceiver-plug.

Extending transversely through the receiverplug on an axis which intersects the longitudinal axis of the recess 33 and which lies in the horizontal plane thereof at substantially right angles thereto is a cylindrical aperture indicated generally at 42, the opposite ends of which intersect the corresponding sides of the receiver-plug and constitute axially-aligned transversely-spacedapart guide-apertures 43 and 44 for the lockinglugs of the receiver-plug as. hereinafter described. The front wall of the transverse aperture 42 intersects the rear end of the counterbore, as shown in Figs. 6, 7 and 8, so as to provide a substantiallystraight bottom edge 45 on the sloping stopshoulder 3l of the counterbore.

The receiver-plug 2li isadapted to be assembled in the sleeve-portion I9 of the receiver, in the Y 4 manner shown in Figs. 1, 2 and 3, that is to say, with a short finger-grip portion 46 of the plug extending rearwardly of the rear end of the receiver so as to enable the shooter to readily grasp the plug to effect its removal from and assembly In its normal assembled position in the receiver, the guide-apertures 43 and 44 of the plug are in axial alignment with corresponding apertures 4l and 48 formed in diametrically-opposi-te sides of the receiver, the forward outer edge of each aperture of the receiver being slabbed off as at 4i?l and 53 respectively to facilitate access to the outer ends of the locking-lugs of the receiver-plug locking-means.

The latter comprises a pair of locking-lugs 5l and 52 and a lug-engaging and restraining-member indicated generally at 53 and hereinafter described. Referring especially to Figs. 2 and 10, the locking-lugs constitute short-cylindrical members having cam-faces 54 and 55 respectively at their inner ends, each cam-face extending from a major diameter on the inner end of its respective'lug forwardly andoutwardly on the front periphery thereof, the slope of each camace making an angle of substantially 45 with the longitudinal axis of its respective lug. The outer Aend of each lug comprises a cylindrical surface of revolution corresponding in radius to the radius of the peripheral surface of the receiver so as to blend smoothly therewith. Moreover, the lugs are provided in their front faces with transverse notches 56 and 5l respectively for limiting the outward radial movement of each lug from its guide-aperture in the receiver-plug. That is to say, when each lug is mounted in its respective guide-aperturev 43 and 44 respectively of the receiver-plug, it is adapted to be permanently held from sliding out of its respective aperture by splaying the outer rim thereof opposite the shoulder of its respective transverse notch, as indicated at 58 and 5S respectively. As shown 'especially well in Figs. 2, 4 and 8, the over-al1 tance substantially equal to the diameter of theY blind aperture 34. Y

As thus spread apart, the outer end of each lug extends into the'apertures 41 and 48 respectively of the receiver to lock the receiver-plug thereto, the curvilinear ends of the lugs being substantially flush with the periphery of the receiver.

The locking-lugs are adapted normally to be held in locking engagement with the receiver by means of the aforementioned lug-engaging-andrestraining member 53 which is shown especially well in Figs. 2, 4 andY 5' and comprises an elongated tubular member having anY enlarged cylindrical head 6G at its rear end, the diameter of which is substantially equal to the diameter of the counterbore 35 whereby the head makes a smooth longitudinally-sliding t therein. The rear end of the head @il is formed with a frustoconical cam-face 3|, the angle of its slope corresponding substantially to the slope of the camfaces 54 and 55 of the respective lugs and to the slope of the shoulder 31 which constitutes a stop for the restraining-member 53. Extending forwardly from the vfront face ofthe head. Se is an` integral collar 62 which at its junction with the head t' is of reduceddiameter corresponding substantially to the internal diameter ofthe action-spring 28 and forms an annular shoulder t?.v with the head @it constituting aseat for the rear end of the action-spring Forwardly of the annular shoulder the diameter c-fthe collar is reduced to provide au second annular shoulder 64 andv a cylinrical shank 6&5v which extends forwardly thereof, the forward end et of the shank constituting a seat for the rear end of the firing-v plunger spring 3i', which as shown clearly in Figs. 1, 4- and 5 is mounted on the firing-plunger 29 and within the action-spring E8. Fitted' see curely on thev collar 62 of thev lug-actuating membert is a cylindrical sleeve o?, the rear end of which abuts against theY annular shoulder Sli' of the collar, the length of the sleeve being' substantially twicev theA length of the restrainingmember' 53 and such that when the latter is in i'ts' normal operating positionas shown in Figs. 1, Zand 4' and the action is closed, the forward end of the sleeve will extend a short way into the open rear' end ofV the longitudinal aperture 2T of the breech-bolt. In this connection, it will be noted that the` outside diameter of the sleeve corresponds substantially to the diameter of the coll'ar 62 and' to the inside diameter of the actionspri'ng 26, asa consequence of which the sleeve serves as a support therefor. Moreover, the in side` diameter of the sleeve' is substantially equal to the outside diameter of the firing-plunger spring 3l and hence constitutes a tubular-guide therefor.

As indicatedv clearly in Fig. 1, when the locking-lug engaging-member 53' is assembled in the forward end of the receiver-plug, the lug-engaging member is adapted normally to be resiliently` held against the stop-shoulder 3l at the top rear edge of the counterbore by the force of the action-spring 23 bot-h when the latter is only partially stressed, that is to say when the action is closed, and when the action-spring is strongly compressed by the rearward displacement of the breech-bolt. in its normal position, the frustoconical cam-face 5! of the lug-engaging member is in conta-et with the respective' cam-faces 5% andi 55A of the locking-lugs so that each lug' resiliently held in its' normal outwardly-projecting position in locking engagement with the receiver, the inner ends of the outwardly-projectinglugsA being spaced apart a distance corresponding substantially to the diameter ofV the blind aperture Sli.

Referring more especially to Figs. l through 4, the ring-plunger 29 constitutes an' elongated cylindrical' rod having an enlarged head 5S at its forward end adapted to extend into the rear end ci? the breech-bolt aperture 21- to engage theV rear end of the firing-pin 25', the diameter of the rod being substantially equal to the inside diameter of the plunger-spring so as to extend` therethrough and support the latter thereon. The' head 58' of the firing-plunger is supportedl freely within the action-spring 28 whereas the rear endfportion of the firing-plunger rod is adapted. tor be slidably supported in the cylindrical' bore' 5S' of the lug-restraining member 53 and in its cocked position to extend through the head of the latter rearwardly into the rear end of the blind aperture 34'; in which position it is adapted` to be engaged and held in its cocked' supported' inv the Sear-slot 38 by a transverse pivot-pineto; To this end, the rear extremity of4 the firing-plunger rod is' formed with a; cylin-i drical stem 'lil 'of reduced diameter joined intee grally to the rear' end of the rod by a conical shoulder 1f ii. Formed integrally at the rear end4 of the stern is' ai' bar-b 'l2' having acyl'i-ndrical skirtV the diameter of which corresponds substantially to' the diameter of" the blind aperture Sf and the bore te: of the lug-engaging member! 53 so as to' slide freely" through these respective axially aligned apertures. The rearend of the barb lil comprises a frusto-conical surface 'M'- for the purpose hereinafter described. The arrnula-r shoulder' 'i5 formed at the juncture of the', rear' end? of the stem 'IS with the skirtl of the barb l2 constitutes the* Sear-shoulder with which the seal' S'tisad'aptecl to engage to lioldthe firingplunger iny its retracted cocked` position,- as shown in' Figs. l and 2. noted by reference to Fig. 2 that when the firingpl'unger is heid inits cocked position, the rear! endor'the firing-plunger rod extends through the;

of the lug-'engaging' memberv 5t suffi'- ciently so that a cylindrical portionA lo of the rod'- in engagement with the opposi-tely disposedV inner endsoff the respective.locking-lugsand constitu-tes a positive stopt to prevent inadvertent re'- tractionof the'lu'gs from locking engagement withY the receiver while the plunger is cocked.

The operation ofn the`r locking: elements of the'L receiver-plug may be described briefly as follows.- Assuming the receiver-plug is insertedv into thel sleeve-portion lf9 therear end of the receiver andI that the lcckingelu'gs 51 and 52' havebeen spread' apart in locking engagementwith the re`- spective apertures and: 43 of the receiver, by engagement of the` frusto'-c'oni'calA camf-face 5 I- of the lug-engaging member 53 with the respective cam-faces 5d and 55 of the lugs, when the rire-A arm is discharged the breech-bolt will move rear.- wardly in the receiver thereby compressing the action-spring 28. Moreover, since the rear end of the firing-pin 25 is in engagement with the head 58 of the ring-plunger Z9, continued rearward movement ofthe breech-bolt eiects the7 rearward' movement of the firing-plunger suchf that its scar-shoulder 15 ai; the rear extremity thereof is moved rearward-ly from its positiony shown in Fig. 4 through the lug-engaging member 53 into the rear end of the blind aperture 34 where it is engaged` bythe sear 3d, the rearward movement of the-ringplunger simultaneously compressing the firing-plunger spring 3l. On theV return of the breech-bolt to its forward breech-closing position, as shown in Fig. 1, the firing-plunger is heldv in its retracted firing position by the= sea-r and on release therefrom isl thrust forwardly by iltscompressed spring 3l tof` drive the head B8 of the plunger' against the rear end of the firingep'in': 25 tofire a fresh cartridge in the chamber of the barrel. As pointed out above, the' action-spring 2t isv adapted to engage and hold the lug-engaging member in its rearmost position against the stop-shoulder 37, both when the action is open and when it is in its'- forward closing position, as a, consequence ofl which the locking-lugs are resiliently held nor1- v In' this connection, it will be that the ring-plunger and the breech-bolt are in their forward positions in the receiver, as indicated in Fig. 4, then in order to dismount the end-closure from the rear end of the receiver, the shooter need but press inwardly radially on the outer ends of the respective locking-lugs to move the outer ends thereof Out of engagement with the apertures 41 and 48 of the receiver. To do so, the forces applied to the outer ends of the locking-lugs must be suiiicient to overcome the resistance exerted by the action-spring against the lug-engaging member 53 so as to move the latter forwardly in the counterbore of the end-closure. Having disengaged the lockinglugs from the apertures of the receiver, the endclosure may then be drawn rearwardly outV of the receiver, as indicated in Fig. 5, carrying with it the locking-lug engaging-member 53, the ring-plunger, the action-spring and the firingplunger spring, Moreover, it should be noted that while theilocking-lugs are pressed inwardly out of locking engagement with the receiver during the removal of the end-closure, the inner ends of the locking-lugs are so close together as to prevent the frusto-conical end 14 of the ring-plunger from engaging therebetween. Consequently, any effort to cock the iirearm while the end-closure is unlocked from the receiver is effectively frustrated. On reinserting the endclosure in the end of the receiver, the lockingelements of the end-closure are retained in the relative positions shown in Fig, until the locking-lugs arrive opposite the apertures 41 and 48 of the receiver, whereupon the force of the compressed action-spring acting against the head of the lug-engaging member 53 to seat the latter against the stop-shoulder 31 cams the lockinglugs outwardly radially into locking engagement with their respective apertures of the receiver, while the inner ends of the lugs are spaced apart, as shown in Fig. 4, so as to permit the ringplunger to move rearwardly into its cocked position in the end-closure. Should the lug-restraining member 53 fail to seat properly against its stop-shoulder 31, then by pressing against the rear end of the end-closure While simultaneously cooking the rearm, the barb 12 of the rearwardly-mcving iiring-plunger would be driven between the inner ends of theV locking-lugs and positively force the latter outwardly into locking engagement with the receiver.

The invention may be carried out in other specic ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range `of the appended claims are intended to be embraced therein.

I claim:

1. In an automatic firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring and a reciprocable breech-bolt mounted in Asaid receiver; an endclosure mounted in the rear end of said receiverV for retaining said action-mechanism therein; andV locking-means to secure said end-closure in said receiver said locking-means comprising elements carried by said end-closure and arranged to move outwardly into locking engagement with said receiver, and an element-restraining member cooperatively associated with said elements and engaged by said action-spring to hold said elements from locking engagement with said receiver, and` an element-restraining member mounted in said end-closure, said element-restraining member being cooperatively associated with said elements and engaged by said action-spring to hold said Y elements outwardly transversely in resilient locking engagement with said receiver.

3. In an automatic firearm including in combination: a receiver; a barrel supported on the forward end of said receiver; action-mechanism including an action-spring and Va reciprocable breech-bolt mounted in said receiver; and endclosure mounted in the rear end of said receiver for retaining said action-mechanism therein; and locking-means to secure said end-closure in said receiver said locking-means comprising lugs supported in said end-closure for transverse movement with respect thereto and having cam-faces on the inner ends thereof, and a lug-restraining member mounted in said end-closure and having a cam-face at its rear end arranged to engage the respective cam-faces of said lugs, said actuatingspring being arranged to engage the forward end of said lug-restraining member normally to urge its cam-face into cooperative engagement with the respective cam-faces of said lugs to hold the outer ends thereof outwardly resiliently in locking engagement with said receiver.

4. In an automatic firearm including in combination: a receiver; a barrel supported on the forward end of said receiver; action-mechanism including an action-spring and a reciprocable Y locking-means to secure said end-closure in said receiver said locking-means comprising'lugs supported in said end-closure for transverse movement with respect thereto, to and from locking engagement with said receiver, and a lug-restraining member mounted in said end-closure, said lug-restraining member being cooperatively associated with said Ylugs and engaged by said action-spring to hold said lugs outwardly resiliently in locking engagement with said receiver; and stop-means on said end-closure arranged to engage 'the outer ends of said lugs to positively hold said lugs from moving transversely beyond the outer walls of said receiver.

5. In an automatic firearm including in combination: a'receiver; a barrel supported on the forward end ci said receiver; action-mechanism including an action-spring and a reciprocable breech-bolt mounted in said receiver; an endclosure mounted in the rear end of said receiver for retainingV said action-mechanism therein; locking-means to secure said end-closure in said receiver said locking-means comprising lugs supported in said end-closure for transverse movement with respect thereto and having cam-faces on the inner ends thereof, and a lug-restraining member mounted in said end-closure and having acsasi s r-acam-iaceat its .rearend arrange'dto engage .the

respective -camefaces yoi said "lugs said actuatingspring -being arranged to .engage the forward :end of said lug-restraining member normally to urge cam-.face into cooperative .eng-agement with the respective cam-faces oi said lugs to hold the youter .ends thereof resiliently in locking engage- -ment with said receiver; Aand stop-.means in said zend-closure to limit the outward movement .of

said lugs therefrom.

6. `In an automatic rearm including in .combination: a receiver; a 'barrel supported in 'the dor-Ward lend of 4said receiver; vactiori-mechanism including an .action-spring and a reciprocable breech-bolt mounted in saidreceiver; and .end- .closure mounted in the rear vend oi saidreceiver to retain said action-mechanism therein said endclosure `having alongitudinal .aperture substantially :coaxial with the 'longitudinal .axis `of said Vreceiver and fa transverse .aperture intersecting :said longitudinal aperture at :substantially right angles thereto; and locking-means to secure Ysaid ,end-closure in said receiver said locking-,means comprising lugs .-slidably mounted in the opposite .endsrespectively .of said transverse aperture for Amcvemeut'to .and from locking engagement with said receiver .and a lug-restraining member Amounted inthe longitudinal aperture of said endclosure in axial .alignment withsaid action-spring and in cooperative engagement with :said -lugs said action-spring being varranged to engage one end ci said 'lug-restraining member thereby `to .urge the opposite end thereof .betweenthe respective inner ends cisaid lugs whereby. the latter are held outwardly in resilient locking engagement `with .said receiver.

7, In an automatic iirearm including in combination: a receiver; a barrel supported in the forward end .of said receiver; action-mechanism including an action-spring and la reciprocable breech-bolt mounted `in said receiver; .an endclesure mounted Yin the rear end of said receiver to retain said action-mechanism therein; `-reccntrcl mechanism including a firing-plunger reciprocably mounted in `said end-closure, a ring-spring supported en said plunger and a sear arranged to hold said vfiring-plunger rearwardly in cockedrpcsiticn in said receiver; and lockingrneans to secure -said enduclosure in said receiver said locking-means comprising lugs carried by said end-closure and a lug-restraining member mounted in said .end-closure and cooperatively associated with said lugs, said action-spring being arranged to engage said lug-restraining member normally tc hold said lugs resiliently in vlocking engagement with said receiver, and said ringplunger being arranged .to .cooperatively engage said lugs When said ring-'plunger is held in its cc-cked position by `said sear to hold said lugs positively in llocking veng-agement with rsaid receiver.

8. In an automatic .rearm including in combination: a receiver; a barrel supported in the forward end of said receiver; .actiorlfmeehanism Yincluding an action-spring and Ya reciprocable breech-bolt mounted insaid receiver; an end-closure mounted in the rear end oi said receiver to :retain `said action-mechanism therein said endclcsure having a longitudinalaperture substantially coaxial with the longitudinal Vairis `of said receiver vand a transverse aperture intersecting `said longitudinal aperture at `substa-ntially right .angles thereto; .nrecontrol mechanism `includ- .,'ng a firing-plunger, .a firing-spring supported .on said plunger'anda sear .mountedin said` Ylon- `gitudinal aperture. and arranged to .hold said v)lring-.plunger `rearwardly in cockedposition in said receiver; and locking-means to secure .said endclcsure in vsaid receiver said locking-means comprising lugs slidab'ly mounted in the .opposite ends respectively .of .said transverse .aperture and having cam-faces on .the'inner ends thereof and a lug-restraining member having .a longitudinal aperture in .which to s-lidably support :said firingplunger said restraining-member being slidably mounted inthe longitudinal yaperture ofy said endclosure .and havingla cam-iaceat its rear end arranged to cooperatively engage 'the respective .cam-faces on the inner ends of said lugs, said action-spring being .arranged to engage the forward end of vsaid lug-restraining member thereby to Wedge its lcam-face between the respective cam-faces of said lugs'normallyto hold the latter resilientlyzoutwardiy in .locking .engagement with said receiver and said iiring-plunger .being Aarranged tc cooperatively engage said lugs when said firing-plunger is held in its cocked .position .by said scar .to holdsaid lugs positively in locking engagement with sai-d receiver.

9. In an automatic firearm 'including in .combination: a receiver; a .barrel supported in .the forward vend of said receiver; .action-mechanism .including an actionespring and a .reciprocable breech-boit mounted :in lsaid receiver; an .endclosure mounted in the rear vend of said receiver to retain said .action-mechanism therein said end-closure having a longitudinal aperture .substantially coaxial with :the longitudinal axis of said receiver anda transverse aperture intersectying said longitudinal .aperture at substantially right angles thereto; yfire-control mechanism including a firing-plunger, a firing-spring supported on said plunger and .a sear mounted in said longitudinal aperture and :arranged to hold said firing-plunger rearwardly in cocked position in said receiver; and locking-means to secure said end-closure in said receiver said locking-means comprising lugs slidably mounted `in the opposite ends respectively oi said transverse aperture and having cam-faces on the inner ends thereof and .a lug-restraining member having a longitudinal aperture in which toslidably support said firing- .plunger said restraining-member being .slidably mounted in the longitudinal aperture of said endclosure and having acam-face at its rear end arranged to cooperatively engage .the respective cara-.faces on the .inner ends of .said lugs, said action-spring being Varranged to .engage the forward end of said lug-restrainingmember thereby to wedge its cam-face between the respective .cam-faces of saidilugs-normally .to hold the latter resilientlyoutwardly in locking vengagement with said receiver and said firing-plunger being arranged to cooperatively engage said lugs when said iring-plunger is held in its cocked position by said scar to 'holdfsaid lugs positively in lockingecngagement ywith said receiver; and stop- `means in the outer ends of said transverse aper .ture to limit the outward movement of'said lugs.

lil. In anautomaticrearm includingrin com- 'binationz a receiver; a barrel supported in the forward end of said receiver; action-mechanism .including an action-spring and a reciprocable `plunger; and locking-emeans'to .secure said end- 11 closure in said receiver said locking-means comprising axially-aligned lugs supported in said end-closure for outward radial movement, and a lug-restraining member slidably mounted in the longitudinal recess of said end-closure and having a longitudinal axial aperture arranged to support said firing-plunger` for longitudinal sliding movement normally between the spaced-apart inner ends of said lugs said action-spring being arranged to engage said lug-restraining member to wedge the rear end thereof between the inner Y ends of said radially-movable lugs so as to hold the said inner ends of said lugs in spaced-apart relationship and the outer ends thereof resiliently in engagement with said receiver and said ring-plunger being arranged to cooperatively engage said lugs when said firing-plunger is held in its cocked position by said sear to hold said lugs positively in locking engagement with said receiver.

11. In an automatic iirearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring and a reciprocable breech-bolt mounted in said receiver; ringmechanism including a sear and a firing-plunger; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism therein said end-closure having a longitudinal recess to receive said sear and said ring-plunger; and locking-means to secure said end-closure in said receiver said locking-means comprising axially-aligned lugs supported in said end-closure for outward radial movement and having cam-faces on the inner ends thereof, and a lug-restraining member slidably mounted in the longitudinal recess of said end-closure and having a longitudinal axial aperture arranged to support said firing-plunger for longitudinal sliding movement normally between the spacedapart inner ends of said lugs and a cam-face at the rear end of said lug-restraining member arranged to cooperatively engage the respectivev cam-faces on the inner ends of said lugs said action-spring being arranged to engage the forward end of said lug-restraining member to wedge its cam-face between the corresponding cam-faces of said radially-movable lugs normally to hold the latter resiliently in spaced-apart relationship and to lockingly engage the outer ends thereof with said receiver and said firingplungei1 being arranged to cooperatively engage said lugs when said firing-plunger is held in its cocked position by said sear to hold said lugs positively in locking engagement with said receiver.

12. In an automatic firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; firing-means including a firing-plunger and a sear arranged to hold said firing-plunger rearwardly in cocked position in said receiver; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism therein; and means carried by said end-closure to lock said end-closure in said receiver the lockingmeans comprising lugs mounted in said endclosure and arranged to be moved outwardly into locking engagement with said receiver, and a lug-restraining member mounted in said end-closure and arranged to be engaged by said actionspring normally to hold said lugs outwardly resiliently in locking engagement with said receiver said ming-plunger being constructed and arranged Yto coact with said lugs when said firingplunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said firearm is cocked.

13. In an automatic firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; firing-means including a firing-plunger and a sear arranged to hold said ring-plunger rearwardly in cocked position in said receiver; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism therein; and means carried by said end-closure to lock said end-closure in said receiver the locking-means comprising lugs mounted in said endclosure and arranged to be moved outwardly into locking engagement with said receiver, each of said lugs having a cam-face at its inner end, and a lug-restraining member mounted in said end-closure and having a cam-face at its rear end arranged to cooperatively engage the respective cam-faces of said lugs, said lug-restraining member being engaged at its forward end by said action-spring whereby the cam-face of said lugrestraining member is wedged normally between the respective cam-faces of said lugs to holdv the outer ends thereof resiliently in locking engagement with said receiver said ring-plunger having an end-portion arranged to engage between the inner ends of said lugs when said ringplunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said rearm is cocked.

14. In an automatic firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; firing-means including a firing-plunger a sear arranged to hold said ring-plunger rearwardly in cocked position in said receiver and a firing-plunger spring; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism therein; and means carried by said end-closure to lock said end-closure in said receiver the locking-means comprising lugs mounted in said end-closure and arranged to be moved into locking engagement with said receiver each of said lugs having a cam-face at its inner end, and a lug-restraining member mounted in said end-closure and having a cam-face at its rear end arranged to cooperatively engage the respective cam-faces of said lugs, said lug-restraining member being engaged at its forward end by said action-spring and said firing-plunger spring whereby the cam-face of said lug-restraining member is wedged normally between the respective cam-faces of said lugs to hold the outer ends thereof resiliently in locking engagement with said receiver said ring-plunger having an end-portion arranged to engage between the inner ends of said lugs when said firing-plunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said firearm is cocked.

15. In an automatic rearm including in cornbination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; firing-means including a firing-plunger and a scar arranged to hold said firing-plunger therein; means carried by said end-closure to lock said end-closure to said receiver the lockingmeans comprising lugs mounted in said end-closure and arranged to be moved outwardly into locking engagement with said receiver, and a lug-restraining member mounted in said endclosure and arranged to be engaged by said actionspring normally to hold said lugs outwardly resiliently in locking engagement with said receiver said firing-plunger being slidably supported within said lug-restraining member and arranged to move between the inner ends of said lugs when said firing-plunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said firearm is cocked.

16. In an automatic rearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; iiring-means including a firing-plunger, a sear arranged to hold said firing-plunger rearwardly in cocked position in said receiver and a firing-spring mounted on said plunger; an endclosure mounted in the rear end of said receiver for retaining said action-mechanism therein said end-closure having a longitudinal recess and a transverse aperture intersecting said longitudinal recess adjacent the forward end thereof and at substantially right angles thereto; and means to lock said end-closure in said receiver the locking-means comprising a pair of lugs mounted in opposite ends respectively of said transverse aperture and arranged to be moved outwardly into locking engagement with said receiver each of said lugs having a cam-face at its inner end, and a lug-restraining member mounted in the longitudinal recess of said end-closure and having a cam-face at its rear end arranged to cooperatively engage the respective cam-faces of said lugs said lug-restraining member being engaged at its forward end by said action-spring and said firingplunger spring whereby the cam-face of said lugrestraining member is wedged normally between the respective cam-faces of said lugs to hold the outer ends thereof resiliently in locking engagement with said receiver said ring-plunger having a portion arranged to engage between the inner ends of said lugs when said firing-plunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said rearm is cocked.

17. In an automatic iirearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an action-spring mounted in said receiver; firing-means including a firing-plunger, a sear arranged to hold said firing-plunger rearwardly in cocked position in said receiver and a firing-spring mounted on said plunger; an endclosure mounted in the rear end of said receiver for retaining said action-mechanism therein said end-closure having a longitudinal recess and a transverse aperture intersecting said longitudinal recess adjacent the forward end thereof and at substantially right angles thereto; means to lock said end-closure in said receiver the lockingmeans comprising a pair of lugs mounted in op- .posite ends respectively of said transverse aperture and arranged to be moved outwardly into locking engagement with said receiver each of said lugs having a cam-face at its inner end, and a lug-restraining member mounted in the longitudinal recess of said end-closure and having a cam-face at its rear end arranged to cooperatively engage the respective cam faces of said lugs said lug-restraining member being engaged at its forward end by said action-spring and said firing-plunger spring whereby the cam-face of said lug-restraining member is wedged normally between the respective cam-faces of said lugs to hold the outer ends thereof resiliently in locking engagement with said receiver said firing-plunger having an end-portion arranged to engage between the inner ends of said lugs when said firing-plunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said firearm is cocked; and stop-means in the outer ends of said transverse aperture to linut the outward movement of said lugs.

18. In a firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism mounted in said receiver; firing-means including a firingplunger, a firing-plunger spring, and a sear arranged to hold said firing-plunger rearwardly in cocked position in said receiver; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism therein; and means carried by said end-closure to lock said end-closure in said receiver the lockingmeans comprising lugs mounted in said end-closure and arranged to be moved outwardly into locking engagement with said receiver, and a lugrestraining member mounted in said end-closure, said lug-restraining member being engaged by said firing-plunger spring and urged thereby between the respective inner ends of said lugs normally to hold said lugs outwardly resiliently in locking engagement with said receiver said ring-plunger being constructed and arranged to coact with said lugs also when said firing-plunger is held by said sear in cocked position in said receiver to preclude inadvertent disengagement of said lugs from said receiver while said firearm is cocked.

19. In a firearm including in combination: a receiver; a barrel supported in the forward end of said receiver; action-mechanism including an apertured breech-bolt reciprocably mounted in the said receiver and an action-spring supported at its forward end in the aperture of said breechbolt; fire-control means including a firingplunger and a ring-plunger spring supported on said firing-plunger; an end-closure mounted in the rear end of said receiver for retaining said action-mechanism and fire-control means therein; and means to lock said end-closure in said receiver said locking-means comprising elements mounted in said end-closure for movement to and from locking engagement with said receiver, and a sleeve-member cooperatively associated with said elements, said sleeve-member being arranged to support the rear end of said actionspring and to support said firing-plunger and said firing-plunger spring within said actionspring.

THOMAS R. ROBINSON, JR`

REFERENCES CITED' UNITED STATES PATENTS Name Date Burton May 20, 1941 Number 

